https://forum.megabass.it/viewtopic.php?f=7&t=93328&p=1101791#p1101791
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Ethelred Kain
Lun 01 Apr, 2019 10:25

Re: Valutazione Yamaha TRB5 1a Serie
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[user]18741[/user],
All'anno di produzione esatto no, però: 
'''
Made in Japan, 1986-1989:
#-letter-#####. 5I04013.
The first number is an internal code. The letter is the month; February (see chart). The next two numbers are the date; 4th. The last three numbers are the unit number; 13. There is no indication of year in this configuration–just “sometime between ’86 and ’89.
'''
Il secondo "numero" in realtà è la lettera O che corrisponde ad Agosto. 

Fonte http://mycoolguitars.com/mij/yamaha-guitars/yamaha-guitar-serial-numbers-dating-your-guitar/


